Block-based data storage systems conventionally include programming and hardware structures to provide block-based access to storage volumes. Such systems may support Fibre Channel, iSCSI (Internet Small Computer System Interface), and/or other block-based protocols. With block-based protocols, a data storage system may receive IO (input/output) requests from “hosts,” i.e., computing devices accessing the data storage system, where the IO requests specify locations to be read from or written to in the form of LUN identifiers (logical unit number, or volume) and particular offset ranges relative to the LUN. IOs that specify read requests map the specified LUNs and offsets to particular locations on disk drives or electronic flash drives, reads the data stored at the mapped locations, and returns the data to the hosts. IOs that specify write requests perform similar mappings, but write the data to the designated locations. The IO requests may return results indicating whether the write requests succeeded or failed. An example of a block-based data storage system is the CLARiiON® system from EMC Corporation of Hopkinton, Mass.
File-based data storage systems include programming and hardware structures to provide file-based access to file systems. File-based data storage systems are sometimes referred to as NAS (Network Attached Storage) systems. Such systems typically support NFS (Network File System), CIFS (Common Internet File System), SMB (Server Message Block), and/or other file-based protocols. With file-based protocols, hosts can issue read and write IO requests by specifying particular file systems, paths, and file names. Internally to the data storage system, file system directories map the files specified by the host IOs to particular sets of blocks on internal volumes, which themselves are derived from disk drives or electronic flash drives. The data storage system accesses the mapped locations and performs the requested reads or writes. An example of a file-based data storage system is the Celerra® system from EMC Corporation of Hopkinton, Mass.
Distributed storage system equipment provides what may be known as data federation including LUN virtualization, cache data coherency maintenance, and data mirroring. An example of such data federation equipment for block-based distributed storage is the VPLEX® system from EMC Corporation of Hopkinton, Mass.